Myotonic dystrophy. A reassessment by conventional and more recently introduced neurophysiological techniques.

A series of complementary neurophysiological investigations was carried out on 24 patients with myotonic dystrophy to determine the extent of nervous system involvement. Conventional electromyography and nerve conduction studies, computerized motor unit number estimation and motor unit potential analysis, vibration threshold studies and a recently introduced technique for heat and cold threshold estimations were undertaken in all patients. The results provide unequivocal evidence of widespread nervous system dysfunction. In many patients there is significant involvement of peripheral large diameter motor and sensory fibres and of small diameter sensory fibres either peripherally and/or centrally. In the light of these results and others reviewed in the literature, the concept of myotonic dystrophy as a pure myopathy can no longer be sustained.